A weekly challenge concerning the interpretation of an algorithm to determine the day on which you were born.

What day of the week were you born on? Do you know? Here's a way to find out.

It's like 'Peaches Today, Peaches Tomorrow' but interestingly generalized.

Can you crack these very difficult challenge ciphers? How might you systematise the cracking of unknown ciphers?

How would you judge a competition to draw a freehand square?

Imagine a strip with a mark somewhere along it. Fold it in the middle so that the bottom reaches back to the top. Stetch it out to match the original length. Now where's the mark?

A geometry lab crafted in a functional programming language. Ported to Flash from the original java at web.comlab.ox.ac.uk/geomlab

Vedic Sutra is one of many ancient Indian sutras which involves a cross subtraction method. Can you give a good explanation of WHY it works?

When in 1821 Charles Babbage invented the `Difference Engine' it was intended to take over the work of making mathematical tables by the techniques described in this article.

However did we manage before calculators? Is there an efficient way to do a square root if you have to do the work yourself?

Can you think like a computer and work out what this flow diagram does?

Is the regularity shown in this encoded message noise or structure?

A sequence of numbers x1, x2, x3, ... starts with x1 = 2, and, if you know any term xn, you can find the next term xn+1 using the formula: xn+1 = (xn + 3/xn)/2 . Calculate the first six terms of this. . . .

This article explains the concepts involved in scientific mathematical computing. It will be very useful and interesting to anyone interested in computer programming or mathematics.

Keep constructing triangles in the incircle of the previous triangle. What happens?

In this short problem, can you deduce the likely location of the odd ones out in six sets of random numbers?

Scheduling games is a little more challenging than one might desire. Here are some tournament formats that sport schedulers use.